This is arguably the golden age for the precise age, metallicity mass estimation of star clusters and galaxies. Bigger telescopes, more sensitive instruments, and wide variety of sky surveys have accumulate high quality datasets while the excellent theoretical models also emerge. From the theoretical perspective, all the new ingredients such as new stellar spectral libraries, significantly more detailed stellar atmosphere models, and new stellar interior models become available lately for the construction of fine stellar population models. In this talk, I will present new stellar population models that incorporate the flexible chemistry. In particular, I demonstrate how surface brightness fluctuation models and some examples of Lick spectralindices are by influenced by element by element variations.